Abstract One of the most serious concerns that have historically dominated discussions of the health care workforce in the US is the persistent, unequal distribution of providers, especially deep shortages of physicians in disadvantaged urban communities, small towns, and rural areas. To address this concern, policymakers have taken considerable efforts during the past half-century. Among the efforts, the National Health Service Corps (NHSC) is the largest and most significant public policy intervention that has been initiated to address the geographic maldistribution of clinician workforce in the nation. The NHSC aims to place health professionals in underserved areas by providing scholarships to students and by repaying educational loans for recent graduates who commit to work in health professional shortage areas (HPSAs). The past decade has witnessed a dramatic increase in federal investment in the NHSC, first through the American Recovery and Reinvestment Act in 2009, and then by the Affordable Care Act in 2010. Several studies have observed that these two Acts have more than doubled the NHSC?s annual budget and led to substantial expansion of the NHSC?s clinician workforce, which has also become more diverse and more evenly distributed across states. However, no study to date has considered the potential effect of the NHSC expansion on disparities in health care and health across geographic areas. Since the NHSC expansion has brought more clinicians to HPSAs, one may expect to see a reduction in health disparities between HPSAs and other areas. Further, while the increased investment has resulted in overall growth of the NHSC?s workforce, the growth varied significantly across specialties, including primary care, mental health, and dental care workforce. Consequently, the effects of the NHSC expansion on health and health care disparities are likely to differ by clinician specialty. This proposed project aims to examine these issues and fill the gap in the literature. To our knowledge, it will be the first study to assess the effect of the recent NHSC expansion on health and health care disparities. The project has the following Specific Aims: Aim 1. To assess the effect of the recent NHSC expansion on disparities in primary care and outcomes. Aim 2. To assess the effect of the recent NHSC expansion on disparities in mental health care and outcomes. Aim 3. To assess the effect of the recent NHSC expansion on disparities in dental health care and outcomes. Aim 4. To assess the effect of the recent NHSC expansion on disparities in patient-reported quality of care. To examine these aims, we will use novel and state-of-the-art data and methods to ensure our findings are robust and valid. The proposed study is unique and timely, and the study findings will be of direct use to policymakers engaged in assessing and modifying the NHSC as part of their efforts to right the maldistribution of the US provider workforce and reduce health disparities.